4x10g

What's the functional difference? The reason I ask is because I have an Arista 7050QX-32-S (24x QSFP+ 4x10G-capable-ports and 8 QSFP+ 40G-only-ports) and recently I picked up some Arista 40G-UNIV transceivers expecting, perhaps niavely, for them to functionally be an SMF/MMF compatable version...